1. Field of the Invention
Aspects of the invention relate to a wireless data communication system. More particularly, aspects of the invention relate to a multi-user data transmission/reception system.
2. Description of the Related Art
Recently, various multimedia services such as a voice service are being provided in a wireless communication environment, and various studies are being conducted to support high-speed and high-quality data transmission in the wireless communication environment. For example, studies of Multiple-Input Multiple-Output (MIMO) systems using a channel in a spatial area are being conducted.
A MIMO system can acquire a channel capacity using a MIMO antenna in a channel environment where scattering is abundant, the channel capacity being in proportion to a fewer number of antennas, from a transmitting antenna and a receiving antenna.
In a multi-user environment where a single base station supports a plurality of terminals, studies regarding a MIMO antenna transmission technique are being conducted to improve all capacities of the MIMO system for multiple users.
There is a difference between the MIMO system for multiple users and a general MIMO system for a single user in that the multiple users transmit data to the same base station on an uplink, and the base station transmits signals to the multiple users on a downlink. Also, the multiple users cannot communicate with one another.
On a downlink channel, each of a plurality of users may receive other users' signals in addition to their own signal due to a signal interference problem that occurs because the base station simultaneously transmits signals to the plurality of users. A technique capable of preventing the signal interference problem may not be applicable to a mobile station due to complexity and costs. However, the signal interference problem can be mitigated by effectively designing a transmission signal in a transmitter of the base station.
Accordingly, a new method capable of selecting an effective transmission mode is required in a data transmission/reception system for multiple users.